This invention relates to photographic exposure control systems and, more particularly, to an exposure control system for artificial illumination in which an aperture value is determined in accordance with scene ranging.
Fully automated, highly compact cameras powered by a small battery located within the camera require efficient, low power shutter drive systems. Additionally, such shutter mechanisms may be called to function within the complex photographic cycle required for a fully automated, single lens reflex camera to carry out viewing operations and the like. A photographic exposure control system designed for such automatic reflex operation is described in a copending application for U.S. patent by Irving Erlichman entitled, "Non-Cocking Springless Shutter Developing Two Parameter Exposure Regulation", Ser. No. 362,926, filed May 22, 1973 and assigned in common herewith. The above-noted application describes an exposure control mechanism in which a stepper motor is utilized to drive a pair of shutter-diaphragm blades in synchronism so as to define a predetermined variation of aperture values over the camera optical path. In this arrangement, the blades are driven through a series of steps or halting positions defining gradual variation in aperture value in accordance with the stepper motor magnetic detents and responsive to successive pulses from a digital network, and exposure regulation is provided by a light sensing network to automatically determine a suitable exposure cycle as a function of scene brightness. It is desirable, however, to utilize a different mode of operation, responsive to scene ranging when the camera is employed under artificial illumination.